Forest investigators busy in the field

If a tree dies in the forest and there's no one around to see it Â that could mean two scientists from the Regional Office of the U.S. Forest Service haven't been called yet.

John Wenz and John Pronos have about 8 millions acres of protected lands to cover Â from Lake Tahoe south to the end of the Sierra Nevada. The two U.S. Forest Service employees spend more than half their time in the woods, trying to discover and prevent the causes of tree mortality on public lands.

Wenz, an entomologist, and Pronos, a plant pathologist, are prepared to help the forests' resource managers with any insect problem or plant disease that comes along.

They share their information with other federal agencies, including the U.S. Bureau of Land Management, the Bureau of Reclamation and the Bureau of Indian Affairs.

Based out of the Stanislaus National Forest Supervisor's Office in Sonora, the two men travel to spots where foresters have reported tree sickness or death.

Their work takes time and attention to detail, but Pronos said he and Wenz can usually figure out the problem.

"Nine times out of 10, we can make a diagnosis on sight," Pronos said.

They take root and bark samples, examine leaves and seek any other evidence they can find.

For example, bark beetles leave behind a distinct pattern in trees, so even though Pronos and Wenz might not see an actual insect, they can still figure out the culprit.

"Often, the problems are not just insects or disease, but a combination of factors," said Wenz. "Drought, for example."

Pronos looks for parasites, such as dwarf mistletoe, which he said can kill a tree or weaken it so it cannot withstand other trauma, like drought or an onslaught of insects.

He checks for signs of disease, and they both look at environmental factors, too, like air pollution.

Wenz compared tree health to that of humans Â it's so much harder to fend off health hazards if people are run down and weak.